Hand-Arm Vibration Syndrome

Hand arm vibration syndrome is a disorder of the blood vessels, nerves and musculoskeletal structures of the hand and arm caused by prolonged exposure to hand-transmitted vibration from power tools. Tools involved include chainsaws, pneumatic drills, grinders, jackhammers, riveters, concrete breakers and vibrating plates. The vascular form is called vibration white finger, secondary Raynaud phenomenon.

Exposure is measured as an 8-hour energy-equivalent acceleration, A(8). A daily exposure of 2.5 m/s2 is the action level, and 5 m/s2 is the limit value. Risk depends on the vibration magnitude, years of exposure, grip force, and cold. Smoking, cardiovascular disease and use of vasoconstrictive drugs raise the risk. Prevalence in exposed workers ranges from 6 to 100%, depending on tool and duration.

Pathology: repeated vibration injures the endothelium and sympathetic control of digital arteries, so vasospasm and later fixed vascular occlusion develop. Nerve damage involves digital nerves and carpal tunnel. Onset is usually after 1 to 15 years of exposure. Progression stops in early stages when exposure ceases, but advanced stages seldom reverse. Complications: digital ulceration, finger necrosis, permanent loss of dexterity and grip, carpal tunnel syndrome, and Dupuytren-like changes.

• Vascular: episodic blanching of fingertips (white), then cyanosis and redness on rewarming, triggered by cold, usually sparing the thumb
• Sensorineural: tingling, numbness, reduced touch and temperature sensation, and clumsiness with buttons and small objects
• Musculoskeletal: grip weakness, pain in the hands and forearms, and bone cysts
• Staging by vascular severity: stage 1 mild (occasional blanching of tips of 1 or more fingers), stage 2 moderate (blanching of distal and middle phalanges), stage 3 severe (extensive blanching of most fingers, frequent attacks) and stage 4 very severe (blanching of whole fingers with trophic skin changes or ulcers)
• Red flags: digital ulceration or gangrene, asymmetrical symptoms, systemic features suggesting connective tissue disease, and fingertip pain at rest

1. Exposure assessment: tool type, daily trigger time, years of use and the manufacturer's vibration values.
2. Clinical examination: nail fold appearance, capillary refill, Allen test, Phalen and Tinel tests, grip strength, two-point discrimination and monofilament testing.
3. Cold provocation test with finger skin temperature or finger systolic pressure measured at 15 and 10 degrees Celsius (a fall in finger systolic pressure of over 20% after cooling is abnormal).
4. Vibration and thermal perception thresholds, and nerve conduction studies for carpal tunnel syndrome or digital neuropathy.
5. Exclusion of other causes: antinuclear antibodies and extractable nuclear antigens, nailfold capillaroscopy (normal in vibration disease, abnormal in scleroderma), cryoglobulins, full blood count, ESR, thoracic outlet and cervical spine assessment, and Doppler of the arm arteries.

Differentials: primary Raynaud phenomenon, scleroderma, cervical radiculopathy, thoracic outlet syndrome, carpal tunnel syndrome and drug-induced vasospasm.

1. Reduce exposure: use low-vibration tools, limit trigger time, rotate tasks, maintain tools, use anti-vibration handles, and avoid a tight grip. Consider cessation of vibratory work in stage 3 and stage 4 disease.
2. Keep warm: gloves, warm clothing and heated handles, and avoid cold exposure.
3. Stop smoking, and avoid caffeine and vasoconstrictive drugs such as beta blockers, ergotamine and decongestants.
4. Drug therapy for troublesome vascular symptoms:
   • Nifedipine modified-release 30 mg orally once daily, increasing to 60 mg once daily (side effects: headache, flushing, ankle edema).
   • Amlodipine 5 to 10 mg orally once daily as an alternative.
   • Losartan 50 mg orally once daily, or sildenafil 50 mg orally 8-hourly, in selected patients, avoiding with nitrates.
5. Severe ischemia or digital ulcers:
   • Iloprost 0.5 to 2 nanograms/kg/min IV infusion for 6 hours daily for 3 to 5 days.
   • Topical glyceryl trinitrate 2% ointment applied to the fingers twice daily.
   • Wound care and antibiotics for infection (flucloxacillin 500 mg orally every 6 hours for 7 days).
   • Digital sympathectomy for refractory ischemia.
6. Carpal tunnel syndrome: wrist splint at night and surgical release when needed.
7. Neuropathic pain: gabapentin 300 mg orally at night, increasing to 900 to 1800 mg daily in divided doses.
8. Health surveillance of exposed workers at hiring and yearly, with a symptom questionnaire and clinical review, and prompt reassessment for any symptoms.

Follow-up every 6 to 12 months. Counsel on exposure limits, protective measures, notification and compensation.